Euv pellicle and mounting method thereof on photo mask

ABSTRACT

In a method of de-mounting a pellicle from a photo mask, the photo mask with the pellicle is placed on a pellicle holder. The pellicle is attached to the photo mask by a plurality of micro structures. The plurality of micro structures are detached from the photo mask by applying a force or energy to the plurality of micro structures before or without applying a pulling force to separate the pellicle from the photo mask. The pellicle is de-mounted from the photo mask. In one or more of the foregoing and following embodiments, the plurality of micro structures are made of an elastomer.

RELATED APPLICATION

This application claims priority to U.S. Provisional Application No.63/056,530 filed on Jul. 24, 2020, the entire disclosure of which isincorporated herein by reference.

BACKGROUND

During an integrated circuit (IC) design, a number of layout patterns ofthe IC, for different steps of IC processing, are generated. The layoutpatterns include geometric shapes corresponding to structures to befabricated on a substrate. The layout patterns may be patterns on a maskthat are projected, e.g., imaged, by a radiation source on a photoresistlayer on the substrate to create the IC. A lithography process transfersthe pattern of the mask to the photoresist layer of the substrate suchthat etching, implantation, or other steps are applied only topredefined regions of the substrate. Transferring the pattern of themask to the photoresist layer may be performed using an extremeultraviolet (EUV) radiation source to expose the photoresist layer ofthe substrate.

BRIEF DESCRIPTION OF THE DRAWING

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIG. 1 shows a schematic view of an extreme ultraviolet (EUV)lithography system with a laser produced plasma (LPP) EUV radiationsource in accordance with some embodiments of the present disclosure.

FIG. 2 shows a schematic view of an EUV lithography exposure tool inaccordance with some embodiments of the present disclosure.

FIG. 3A is a plan view and FIG. 3B is a cross-sectional view of areflective photo mask with a pellicle in accordance with someembodiments of the present disclosure.

FIGS. 4A and 4B show various views of pellicle mounting structuresaccording to some embodiments of the present disclosure.

FIGS. 5A, 5B, 5C and 5D show pellicle mounting and dismountingoperations in accordance with some embodiments of the presentdisclosure.

FIGS. 6A, 6B, 6C, 6D, 6E and 6F show pellicle mounting and dismountingoperations in accordance with some embodiments of the presentdisclosure. FIGS. 6G, 6H, 6I, 6J and 6K show pellicle mounting anddismounting operations in accordance with some embodiments of thepresent disclosure.

FIGS. 7A, 7B, 7C and 7D show pellicle mounting and dismountingoperations in accordance with some embodiments of the presentdisclosure.

FIGS. 8A, 8B, 8C, 8D, 8E, 8F and 8G show pellicle mounting anddismounting operations in accordance with some embodiments of thepresent disclosure.

FIGS. 9A, 9B, 9C and 9D show pellicle mounting and dismountingoperations in accordance with some embodiments of the presentdisclosure.

FIGS. 10A, 10B, 10C, 10D, 10E and 10F show pellicle mounting anddismounting operations in accordance with some embodiments of thepresent disclosure.

FIGS. 11A, 11B, 11C and 11D show pellicle mounting and dismountingoperations in accordance with some embodiments of the presentdisclosure.

FIGS. 12A, 12B, 12C, 12D, 12E and 12F show pellicle mounting anddismounting operations in accordance with some embodiments of thepresent disclosure.

FIGS. 13A, 13B, 13C and 13D show pellicle mounting and dismountingoperations in accordance with some embodiments of the presentdisclosure.

FIGS. 14A, 14B, 14C, 14D, 14E and 14F show pellicle mounting anddismounting operations in accordance with some embodiments of thepresent disclosure.

FIG. 15 is a flowchart of pellicle mounting and dismounting operationsin accordance with some embodiments of the present disclosure.

FIG. 16A shows a flowchart of a method making a semiconductor device,and FIGS. 16B, 16C, 16D and 16E show a sequential manufacturingoperation of a method of making a semiconductor device in accordancewith embodiments of present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly. In addition, the term“being made of” may mean either “comprising” or “consisting of” In thepresent disclosure, a phrase “one of A, B and C” means “A, B and/or C”(A, B, C, A and B, A and C, B and C, or A, B and C), and does not meanone element from A, one element from B and one element from C, unlessotherwise described. Materials, configurations, dimensions, structures,conditions and operations explained with respect to one embodiments canbe employed in the other embodiments, and some of the explanations maybe omitted.

A pellicle is a thin transparent film stretched over a frame that isattached with an adhesive over one side of a photo mask (also known as areticle) to protect the photo mask from damage, dust, and/or moisture.Further, when an EUV photo mask is covered by a pellicle, particles willsettle on the pellicle instead of the EUV photo mask and, thus, when thepatterns on the EUV photo mask are imaged on a substrate, the particlesthat are not in the plane of the EUV photo mask do not create a focusedimage on the substrate. It is desirable that the pellicle is highlytransparent to the radiation source of the lithography process. In EUVlithography, the pellicle is should be highly transparent in the EUVwavelength region and have high durability.

In some embodiments, when the pellicle is placed, e.g., mounted, on topof the EUV photo mask, the pellicle is placed on top of a plurality ofadhesive studs or fixtures and a distance between about 2 mm to about 5mm is created between the EUV photo mask and the pellicle. Thus, in someembodiments, one or more openings is created by the distance between theEUV photo mask and the pellicle. In some embodiments, the pellicle isattached to a mounting fixture and the mounting fixture is attached overthe EUV photo mask with a number of adhesive studs, e.g., four studs atthe four corners of the EUV photo mask. Alternatively, the distancebetween the EUV photo mask and the pellicle may be fully sealed and noopening is created by the distance between the EUV photo mask and thepellicle.

FIG. 1 shows a schematic view of an EUV lithography system with a laserproduced plasma (LPP) EUV radiation source in accordance with someembodiments of the present disclosure. The EUV lithography systemincludes an EUV radiation source 100 (an EUV light source) to generateEUV radiation, an exposure device 200, such as a scanner, and anexcitation laser source 300. As shown in FIG. 1, in some embodiments,the EUV radiation source 100 and the exposure device 200 are installedon a main floor MF of a clean room, while the excitation laser source300 is installed in a base floor BF located under the main floor. Eachof the EUV radiation source 100 and the exposure device 200 are placedover pedestal plates PP1 and PP2 via dampers DMP1 and DMP2,respectively. The EUV radiation source 100 and the exposure device 200are coupled to each other by a coupling mechanism, which may include afocusing unit. In some embodiments, a lithography system includes theEUV radiation source 100 and the exposure device 200.

The lithography system is an EUV lithography system designed to expose aresist layer by EUV light (also interchangeably referred to herein asEUV radiation). The resist layer is a material sensitive to the EUVlight. The EUV lithography system employs the EUV radiation source 100to generate EUV light, such as EUV light having a wavelength rangingbetween about 1 nm and about 50 nm. In one particular example, the EUVradiation source 100 generates EUV light with a wavelength centered atabout 13.5 nm. In the present embodiment, the EUV radiation source 100utilizes a mechanism of laser-produced plasma (LPP) to generate the EUVradiation.

The exposure device 200 includes various reflective optical components,such as convex/concave/flat mirrors, a mask holding mechanism includinga mask stage, and wafer holding mechanism, e.g., a substrate holdingmechanism. The EUV radiation generated by the EUV radiation source 100is guided by the reflective optical components onto a mask secured onthe mask stage. In some embodiments, the mask stage includes anelectrostatic chuck (e-chuck) to secure the mask. Because gas moleculesabsorb EUV light, the lithography system for the EUV lithographypatterning is maintained in a vacuum or a-low pressure environment toavoid EUV intensity loss. The exposure device 200 is described in moredetails with respect to FIG. 2. In some embodiments, an EUV photo maskis transferred into the exposure device 200. As noted, the exposuredevice 200 is maintained under a vacuum environment and the EUV photomask is mounted over a substrate, with a photo resist layer disposed onthe substrate. The EUV photo mask has a pellicle mounted over the EUVphoto mask. After transferring the EUV photo mask with the pellicle intothe exposure device 200, the air pressure in the enclosure between theEUV photo mask and the pellicle is equalized with the vacuum environmentof the exposure device 200 through the holes in the mounting fixture(the frame). The EUV radiation generated by the EUV radiation source 100is directed by the optical components to project the mask on the photoresist layer of the substrate. In some embodiments, after the exposureof the mask on the photo resist layer of the substrate, the EUV photomask with the pellicle is transferred out of the exposure device 200.After transferring the EUV photo mask with the pellicle out of theexposure device 200, the air pressure in the enclosure between the EUVphoto mask and the pellicle is equalized with the atmospheric pressureoutside the exposure device 200 through the holes in the mountingfixture.

In the present disclosure, the terms mask, photo mask and reticle areused interchangeably. In addition, the term resist and photoresist areused interchangeably. In some embodiments, the mask is a reflectivemask. In some embodiments, the mask includes a substrate with a suitablematerial, such as a low thermal expansion material or fused quartz. Invarious examples, the material includes TiO₂ doped SiO₂, or othersuitable materials with low thermal expansion. The mask includesmultiple reflective layers (ML) deposited on the substrate. The MLincludes a plurality of film pairs, such as molybdenum-silicon (Mo/Si)film pairs (e.g., a layer of molybdenum above or below a layer ofsilicon in each film pair). Alternatively, the ML may includemolybdenum-beryllium (Mo/Be) film pairs, or other suitable materialsthat are configurable to highly reflect the EUV light. The mask mayfurther include a capping layer, such as ruthenium (Ru), disposed on theML for protection. The mask further includes an absorption layer, suchas a tantalum boron nitride (TaBN) layer, deposited over the ML. Theabsorption layer is patterned to define a layer of an integrated circuit(IC). Alternatively, another reflective layer may be deposited over theML and is patterned to define a layer of an integrated circuit, therebyforming an EUV phase shift mask. The mask is described with respect toFIGS. 3A and 3B.

The exposure device 200 includes a projection optics module for imagingthe pattern of the mask on to a semiconductor substrate with a resistcoated thereon secured on a substrate stage of the exposure device 200.The projection optics module generally includes reflective optics. TheEUV radiation (EUV light) directed from the mask, carrying the image ofthe pattern defined on the mask, is collected by the projection opticsmodule, thereby forming an image on the resist.

In various embodiments of the present disclosure, the semiconductorsubstrate is a semiconductor wafer, such as a silicon wafer or othertype of wafer to be patterned. The semiconductor substrate is coatedwith a resist layer sensitive to the EUV light in presently disclosedembodiments. Various components including those described above areintegrated together and are operable to perform lithography exposingprocesses. The lithography system may further include other modules orbe integrated with (or be coupled with) other modules.

As shown in FIG. 1, the EUV radiation source 100 includes a dropletgenerator 115 and a LPP collector mirror 110, enclosed by a chamber 105.The droplet generator 115 generates a plurality of target droplets DP,which are supplied into the chamber 105 through a nozzle 117. In someembodiments, the target droplets DP are tin (Sn), lithium (Li), or analloy of Sn and Li. In some embodiments, the target droplets DP eachhave a diameter in a range from about 10 microns (μm) to about 100 μm.For example, in an embodiment, the target droplets DP are tin droplets,each having a diameter of about 10 μm, about 25 μm, about 50 μm, or anydiameter between these values. In some embodiments, the target dropletsDP are supplied through the nozzle 117 at a rate in a range from about50 droplets per second (i.e., an ejection-frequency of about 50 Hz) toabout 50,000 droplets per second (i.e., an ejection-frequency of about50 kHz). For example, in an embodiment, target droplets DP are suppliedat an ejection-frequency of about 50 Hz, about 100 Hz, about 500 Hz,about 1 kHz, about 10 kHz, about 25 kHz, about 50 kHz, or anyejection-frequency between these frequencies. The target droplets DP areejected through the nozzle 117 and into a zone of excitation ZE (e.g., atarget droplet location) at a speed in a range from about 10 meters persecond (m/s) to about 100 m/s in various embodiments. For example, in anembodiment, the target droplets DP have a speed of about 10 m/s, about25 m/s, about 50 m/s, about 75 m/s, about 100 m/s, or at any speedbetween these speeds.

The excitation laser beam LR2 generated by the excitation laser source300 is a pulsed beam. The laser pulses of laser beam LR2 are generatedby the excitation laser source 300. The excitation laser source 300 mayinclude a laser generator 310, laser guide optics 320 and a focusingapparatus 330. In some embodiments, the laser generator 310 includes acarbon dioxide (CO₂) or a neodymium-doped yttrium aluminum garnet(Nd:YAG) laser source with a wavelength in the infrared region of theelectromagnetic spectrum. For example, the laser source 310 has awavelength of 9.4 μm or 10.6 μm in an embodiment. The laser light beamLR0 generated by the excitation laser source 300 is guided by the laserguide optics 320 and focused, by the focusing apparatus 330, into theexcitation laser beam LR2 that is introduced into the EUV radiationsource 100. In some embodiments, in addition to CO₂ and Nd:YAG lasers,the laser beam LR2 is generated by a gas laser including an excimer gasdischarge laser, helium-neon laser, nitrogen laser, transversely excitedatmospheric (TEA) laser, argon ion laser, copper vapor laser, KrF laseror ArF laser; or a solid state laser including Nd:glass laser,ytterbium-doped glasses or ceramics laser, or ruby laser. In someembodiments, a non-ionizing laser beam LR1 is also generated by theexcitation laser source 300 and the laser beam LR1 is also focused bythe focusing apparatus 330.

In some embodiments, the excitation laser beam LR2 includes a pre-heatlaser pulse and a main laser pulse. In such embodiments, the pre-heatlaser pulse (interchangeably referred to herein as the “pre-pulse) isused to heat (or pre-heat) a given target droplet to create alow-density target plume with multiple smaller droplets, which issubsequently heated (or reheated) by a pulse from the main laser (mainpulse), generating increased emission of EUV light compared to when thepre-heat laser pulse is not used.

In various embodiments, the pre-heat laser pulses have a spot size about100 μm or less, and the main laser pulses have a spot size in a range ofabout 150 μm to about 300 μm. In some embodiments, the pre-heat laserand the main laser pulses have a pulse-duration in the range from about10 ns to about 50 ns, and a pulse-frequency in the range from about 1kHz to about 100 kHz. In various embodiments, the pre-heat laser and themain laser have an average power in the range from about 1 kilowatt (kW)to about 50 kW. The pulse-frequency of the excitation laser beam LR2 ismatched with the ejection-frequency of the target droplets DP in anembodiment.

The laser beam LR2 is directed through windows (or lenses) into the zoneof excitation ZE. The windows adopt a suitable material substantiallytransparent to the laser beams. The generation of the laser pulses issynchronized with the ejection of the target droplets DP through thenozzle 117. As the target droplets move through the excitation zone, thepre-pulses heat the target droplets and transform them into low-densitytarget plumes. A delay between the pre-pulse and the main pulse iscontrolled to allow the target plume to form and to expand to an optimalsize and geometry. In various embodiments, the pre-pulse and the mainpulse have the same pulse-duration and peak power. When the main pulseheats the target plume, a high-temperature plasma is generated. Theplasma emits EUV radiation, which is collected by the collector mirror110. The collector mirror 110, an EUV collector mirror, further reflectsand focuses the EUV radiation for the lithography exposing processesperformed through the exposure device 200. A droplet DP that does notinteract with the laser pulses is captured by the droplet catcher 85.

One method of synchronizing the generation of a pulse (either or both ofthe pre-pulse and the main pulse) from the excitation laser with thearrival of the target droplet in the zone of excitation is to detect thepassage of a target droplet at given position and use it as a signal fortriggering an excitation pulse (or pre-pulse). In this method, if, forexample, the time of passage of the target droplet is denoted by to, thetime at which EUV radiation is generated (and detected) is denoted byt_(rad), and the distance between the position at which the passage ofthe target droplet is detected and a center of the zone of excitation isd, the speed of the target droplet, v_(dp), is calculated as

v _(dp) =d/(t _(rad-to))   equation (1).

Because the droplet generator 115 is expected to reproducibly supplydroplets at a fixed speed, once v_(dp) is calculated, the excitationpulse is triggered with a time delay of d/v_(dp) after a target dropletis detected to have passed the given position to ensure that theexcitation pulse arrives at the same time as the target droplet reachesthe center of the zone of excitation. In some embodiments, because thepassage of the target droplet is used to trigger the pre-pulse, the mainpulse is triggered following a fixed delay after the pre-pulse. In someembodiments, the value of target droplet speed v_(dp) is periodicallyrecalculated by periodically measuring t_(rad), if needed, and thegeneration of pulses with the arrival of the target droplets isresynchronized.

FIG. 2 shows a schematic view of an EUV lithography (EUVL) exposure toolin accordance with some embodiments of the present disclosure. The EUVLexposure tool of FIG. 2 includes the exposure device 200 that shows theexposure of photoresist coated substrate, a target semiconductorsubstrate 210, with a patterned beam of EUV light. The exposure device200 is an integrated circuit lithography tool such as a stepper,scanner, step and scan system, direct write system, device using acontact and/or proximity mask, etc., provided with one or more optics205 a, 205 b, for example, to illuminate a patterning optic, such as aEUV photo mask, e.g., a reflective mask 205 c, with a beam of EUV light,to produce a patterned beam, and one or more reduction projection optics205 d, 205 e, for projecting the patterned beam onto the targetsemiconductor substrate 210. A mechanical assembly (not shown) may beprovided for generating a controlled relative movement between thetarget semiconductor substrate 210 and patterning optic, e.g., areflective mask 205 c. As further shown, the EUVL exposure tool of FIG.2, further includes the EUV radiation source 100 including a plasmaplume 23 at the zone of excitation ZE emitting EUV light in the chamber105 that is collected and reflected by a collector mirror 110 into theexposure device 200 to irradiate the target semiconductor substrate 210.In some embodiments, a pressure inside the exposure device 200 is sensedby a pressure sensor 208 inside the exposure device 200 and iscontrolled by a vacuum pressure controller 206 that is coupled to theexposure device 200.

As noted above, because gas molecules absorb EUV light, the lithographysystem for the EUV lithography patterning, e.g. the exposure device 200,is maintained in a vacuum environment to avoid EUV intensity loss. Aftertransferring the EUV photo mask with the pellicle into the exposuredevice 200, the air pressure in the enclosure between the EUV photo maskand the pellicle is equalized with the vacuum environment of theexposure device 200 through the holes in the mounting fixture (theframe) and, thus, vacuum is produced in the enclosure between the EUVphoto mask and the pellicle. In some embodiments, after the exposure ofthe mask on the photo resist layer of the substrate, the EUV photo maskwith the pellicle, the EUV photo mask structure, is transferred out ofthe exposure device 200. After transferring the EUV photo mask with thepellicle out of the exposure device 200, the vacuum in the enclosurebetween the EUV photo mask and the pellicle is equalized with theatmospheric pressure outside the exposure device 200 through the holesin the mounting fixture and, thus, atmospheric pressure in produced inthe enclosure between the EUV photo mask and the pellicle.

FIG. 3A is a plan view and FIG. 3B is a cross-sectional view of areflective EUV photo mask with a pellicle in accordance with someembodiments of the present disclosure.

The reflective EUV photo mask 10 is covered by a pellicle 20 as shown inFIGS. 3A and 3B. The EUV photo mask 10 includes a substrate, reflectivemultiple layers (ML) that are deposited on the substrate, a conductivebackside coating, a capping layer disposed on the reflective ML, and anabsorption layer on the capping layer. In some embodiments, the materialof the substrate 30 includes TiO₂ doped SiO₂, or other suitablematerials with low thermal expansion. In some embodiments, the substrateincludes fused quartz and has a thickness between about 6 mm to about 7mm. In some embodiments, the ML includes a plurality of film pairs, suchas molybdenum-silicon (Mo/Si) film pairs (e.g., a layer of molybdenumlayer above or below a layer of silicon layer in each film pair). Insome embodiments, the ML has 40 to 50 pairs of the molybdenum layer andthe silicon layer and each molybdenum layer has a thickness of 3 nm andeach silicon layer has a thickness of 4 nm. Thus, in some embodiments,the ML has a thickness between 280 nm to 350 nm. Alternatively, the MLmay include molybdenum-beryllium (Mo/Be) film pairs, or other suitablematerials that are configured to highly reflect the EUV light. Thecapping layer may include ruthenium (Ru) and may be disposed on the MLfor protection and may have a thickness of 2.5 nm. In some embodiments,the capping layer may include Ru or silicon (Si) and may be disposed onthe ML for protection and may have a thickness of 4 nm. In someembodiments, the absorption layer that includes a tantalum boron nitride(TaBN) layer is deposited over the ML and the capping layer. In someembodiments, the absorption layer is patterned with pattern features todefine a layout pattern for layer of an integrated circuit (IC). In someembodiments, the backside coating includes chromium nitride (CrN) ortantalum boride (TaB) and has a thickness of 20 nm to 100 nm. In someembodiments, another reflective layer may be deposited over the ML andis patterned to define a layer of an integrated circuit, thereby formingan EUV phase shift EUV photo mask. In some embodiments, the absorptionlayer 45 includes one or a combination of TaBO, TaBN, TaNO, and TaN andhas a thickness between 50 nm and 70 nm.

In some embodiments, a pellicle 20 includes a EUV transmissive membrane22 that includes multiple layers of, for example, a semiconductormaterial, such as Si, SiC or SiGe; a metal alloy, such as silicide (WSi,NiSi, TiSi, CoSi, MoSi, ZrSi, NiZrSi, etc.); a dielectric material, suchas silicon nitride; and a metal material, such as Mo, Zr, Nb, B, Ti orRu, or other suitable material. In some embodiments, the pellicle 20includes a frame 24 having an opening. The pellicle 20 is mounted on theEUV photo mask 10 by attaching the frame 24 to the EUV photo mask 10 viathe adhesive or glue structure 25.

Mounting the pellicle 20 to the EUV photo mask 10 is generally performedby applying a press force to press the pellicle 10 against the EUV photomask 10, in particular to a pressure sensitive adhesive material.De-mounting the pellicle 20 from the EUV photo mask 10 is generallyperformed by applying a pull force to overcome the glue or adhesiveforce of the adhesive material. In the mounting and de-mountingoperations, it is desirable not to leave any residue of the adhesivematerial on the EUV photo mask. Further, it is desirable to reduce theapplying a force and/or a pull force to decrease mounting and/orde-mounting operation time and to avoid rupturing of the pellicle and/orthe EUV photo mask. In the following embodiments, structures andprocesses to mount and de-mount a pellicle to and from an EUV photomask, which can improve the mounting and/or de-mounting operation of thepellicle are explained.

FIGS. 4A and 4B show various views of pellicle mounting structuresaccording to some embodiments of the present disclosure.

In some embodiments, the adhesive structure 25 includes a plurality ofmicro structures 28. The micro structures 28 are stubs, fibers,protrusions, pillars, columns, wedges, and/or cones. The plurality ofmicro structures 28 are regularly or randomly arranged spaced apart fromeach other. In some embodiments, the average diameter of each of themicro structures 28 is in a range from about 0.5 μm to about 500 μm, andis in a range from about 2 μm to about 200 μm in other embodiments. Thespace between adjacent micro structures 28 is in a range from about 1 μmto about 10,000 μm in some embodiments, and is in a range from about 10μm to about 1000 μm in other embodiments. In some embodiments, thenumber of the micro structures 28 per unit area is in a range from 1pieces/mm² to about 10,000 pieces/mm², and is in a range from 10pieces/mm² to about 1000 pieces/mm² in other embodiments. In someembodiments, the smaller the area of the ends of the micro structure tobe attached to the photo mask 10 is, the greater the number of the microstructures. In some embodiments, the area A times the number N (AN) isabout 0.01 to about 10. When AN is too large, the adhesion force exceedsa required threshold, and it may be difficult to remove the pelliclefrom the phot mask. When AN is too small, the adhesion force may beinsufficient.

In some embodiments, the length of the micro structures 28 as attachedto the EUV photo mask 10 is in a range from about 1 μm to about 20,000μm, and is in a range from about 10 μm to about 1000 μm in otherembodiments, and yet in other embodiments, the length is in a range fromabout 40 μm to about 500 μm. When the length is too small, it may take alonger time to reach a pressure equilibrium state in an EUV scanner.When the length is too large, the effect of pellicle protection may bedegraded. In some embodiments, the length D1 of the micro structures 28before attaching to the EUV photo mask 10 is about 10-40% longer thanthe length D1. When the micro structures are too thin and/or too little,the adhesive strength is too low and the pellicle may not be stablyfixed on the EUV photo mask. When the micro structures are too thickand/or too many, the adhesive strength is too large and the pelliclemounting and/or de-mounting operations may be difficult (requiringhigher force). When the micro structures are too short, tolerance in theforce in the mounting and/or de-mounting operation is too small, andwhen the micro structures are too long, the pellicle may not be stablymounted on the EUV photo mask. The micro structures are attached orfixed to the surface of the photo mask 10 via Van der Waals force insome embodiments.

In some embodiments, as shown in FIG. 4A, the plurality of microstructures 28 protrude from a base layer 26 made of the same ordifferent material as the micro structures. In some embodiments, anadhesive layer 27 made of a different material than the base layer 26and/or the micro structures 28 is disposed between the adhesivestructure 25 and the frame 24 as shown in FIG. 4B.

In some embodiments, the plurality of micro structures 28 are made of anelastomer, such as polydimethylsiloxane (PDMS), polyurethane (PU),polymethyl methacrylate (PMMA), polypropylene (PP), polyurethaneacrylate (PUA), or fluorocarbon (such as, polytetrafluoroethylene); ashape memory polymer; a magnetic elastomer; carbon nanotubes (CNT), orother suitable material.

FIGS. 5A, 5B, 5C and 5D show pellicle mounting and dismountingoperations in accordance with some embodiments of the presentdisclosure. FIGS. 6A, 6B, 6C, 6D, 6E and 6F also show pellicle mountingand dismounting operations in accordance with some embodiments of thepresent disclosure.

In some embodiments, the micro structures are a plurality of microfibers 28A as shown in FIG. 5A. In some embodiments, the averagediameter of each of the micro fibers 28A is in a range from about 0.5 μmto about 500 μm, and is in a range from about 2 μm to about 200 μm inother embodiments. In order to mount the pellicle 20 to the EUV photomask 10, the micro fibers 28A are pressed against the surface of the EUVphoto mask 10 such that the ends of the fibers are attached to thesurface of the photo mask 10, as shown in FIG. 5B. In some embodiments,the pressing force (pressure) is in a range from about 0.01 N/cm² toabout 1.0 N/cm². If the pressing force is smaller than this range thepellicle may not be fixed to the EUV photo mask, and if the pressingforce is larger than this range, the fibers may be bent and may not befixed to the EUV photo mask. In order to de-mount the pellicle 20 fromthe EUV photo mask 10, the pellicle is pressed against the EUV photomask (or the photo mask 10 is pressed against the pellicle, or both)before the pellicle 20 is pulled from the EUV photo mask 10 or withoutpulling the pellicle. As shown in FIGS. 5C and 5D, by pressing thepellicle 20 against the photo mask 10 so as to decrease the distancebetween the pellicle 20 and the photo mask 10, the plurality of fibersare bent such that the ends of the fibers are detached from the surfaceof the photo mask 10. Once the ends of the fibers 28A are detached bybending, the pellicle 20 can be easily de-mounted from the photo mask 10with minimum pull force. As set forth above, a pressing force is appliedin the de-mounting operation before or without applying a pulling forceto separate the pellicle 20 from the photo mask 10.

FIGS. 6A-6C and 6D-6F also show more details of pellicle mounting anddismounting operations, respectively, of FIGS. 5A-5D, in accordance withsome embodiments of the present disclosure.

In a mounting operation, as shown in FIG. 6A, a pellicle 20 is supportedby a pellicle holder 120, and an EUV photo mask 10 is supported by amask holder 130 in a pellicle mounting apparatus. In some embodiments,the EUV photo mask 10 is placed on the mask holder 130 facing down andthe pellicle is held by the pellicle holder 120 facing up. Then, asshown in FIG. 6B, the pellicle holder moves up toward the photo mask 10and further toward a mask retainer 100 so that the photo mask 10 abutsthe mask retainer. As shown in FIG. 5B, the ends of the micro fibers 28Aare attached to the photo mask 10 during and as a result of the movementof the pellicle holder 120. Then, as shown in FIG. 6C, the pellicleholder 120 moves down so that the photo mask 10 with the pellicle 20 isplaced on the mask holder 130.

In a de-mounting operation, the photo mask 10 with the pellicle 20 isplaced on the mask holder 130, as shown in FIG. 6D. Then, as shown inFIG. 6E, the pellicle holder 120 moves up toward the photo mask 10 withthe pellicle 20, and further toward the mask retainer 100 so that thephoto mask 10 abuts the mask retainer. As shown in FIG. 5C, the pellicleholder 120 presses the pellicle 20 so that the plurality of fibers arebent. Then, as shown in FIG. 6F, the pellicle holder 120 moves down sothat the photo mask 10 without the pellicle 20 is placed on the maskholder 130.

In other embodiments, pellicle holder 121 supports the side faces of thepellicle as shown in FIGS. 6G-6K. FIGS. 6G-6K show a de-mountingoperation. FIGS. 6H and 6J are plan views. In some embodiments, the maskholder 101 holds the photo mask 10 with a pellicle 20 as shown in FIG.6G. Forks of the pellicle holder 121 are attached to the side faces ofthe pellicle 20. Then, the pellicle holder 121 moves the pellicle 20against the photo mask 10 to release the micro fibers from the surfaceof the photo mask 10 as shown in FIGS. 6I and 6J. Then, the pellicleholder 121 moves down to de-mount the pellicle 20 as shown in FIG. 6K.In some embodiments, instead of or in addition to the vertical movementof the pellicle holder, the photo mask holder vertically moves (i.e.,relative movement to each other).

FIGS. 7A, 7B, 7C and 7D show pellicle mounting and dismountingoperations in accordance with some embodiments of the presentdisclosure.

In some embodiments, the micro structures are a plurality of micro cones28B having a bottom disposed on the base layer 26 and a top, as shown inFIG. 7A. In some embodiments, the top of the cones has a width ordiameter W1 in a range from about 0.5 μm to about 500 μm, or in a rangefrom about 2 μm to about 200 μm in other embodiments. In someembodiments, the cone has a circular or an elliptical bottom in planview and in other embodiments, the cone has a rectangular or a squarebottom in plan view. In some embodiments, a ratio between the top widthW1 and the bottom width W2 (W2/W1) is in a range from about 1 (i.e.,column shape) to about 100 and is in a range from about 5 to about 20 inother embodiments.

In some embodiments, the micro cones 28B are made of shape memoryelastomer, which returns the original shape by applying heat to thedeformed shapes. In order to mount the pellicle 20 to the EUV photo mask10, the micro cones 28B are pressed against the surface of the EUV photomask 10 such that the tops of the cones are deformed to have asufficient contact area and are attached to the surface of the photomask 10, as shown in FIG. 7B. Then, heat is applied to the micro conesat a temperature higher than the threshold temperature Tg. In someembodiments, Tg is in a range from about 50° C. to 110° C. depending thematerial. In order to de-mount the pellicle 20 from the EUV photo mask10, the cones are heated at the temperature higher than the thresholdtemperature Tg before the pellicle 20 is pulled from the EUV photo mask10 or without pulling the pellicle. As shown in FIGS. 7C and 7D, byheating the cones, the plurality of cones return to their original shapeto decrease the contact area, and thus the ends (tops) of the cones aredetached from the surface of the photo mask 10. Once the ends of thecones 28B are detached by heating, the pellicle 20 can be easilyde-mounted from the photo mask 10 with a minimum pull force. As setforth above, heat is applied in the de-mounting operation before orwithout applying the pulling force to separate the pellicle 20 from thephoto mask 10. In some embodiments, the heat is applied from a heaterdisposed in the pellicle holder or the mask retainer, and in otherembodiments, an energy beam, for example an infrared light beam, isapplied to the pellicle or the photo mask, or directly to the microcones. In other embodiments, the atmosphere around the photo mask isheated or heated gas is applied to the photo mask and the pellicle.

FIGS. 8A-8D and 8E-8G also show more details of the pellicle mountingand dismounting operations, respectively, of FIGS. 7A-7D, in accordancewith some embodiments of the present disclosure.

In a mounting operation, as shown in FIG. 8A, a pellicle 20 is supportedby a pellicle holder 120, and a EUV photo mask 10 is supported by a maskholder 130 in a pellicle mounting apparatus. In some embodiments, theEUV photo mask 10 is placed on the mask holder 130 facing down and thepellicle is held by the pellicle holder 120 facing up. Then, as shown inFIG. 8B, the pellicle holder moves up toward the photo mask 10 andfurther toward a mask retainer 100 so that the photo mask 10 abuts themask retainer. As shown in FIG. 7B, the ends of the micro cones 28B areattached to the photo mask 10 during and as a result of the movement ofthe pellicle holder 120. Then, as shown in FIG. 8B, heat is applied fromthe pellicle holder 120 to the micro cones 28 at the temperature higherthan the threshold temperature Tg, in some embodiments. In otherembodiments, the heat is applied from the photo mask holder 100. Then,while the cones are deformed and attached to the photo mask, thetemperature of the cones is decreased (cooled down) below the thresholdtemperature Tg (e.g., 25° C.) as shown in FIG. 8C. Then, the pellicleholder 120 moves down so that the photo mask 10 with the pellicle 20 isplaced on the mask holder 130 as shown in FIG. 8D.

In a de-mounting operation, the photo mask 10 with the pellicle 20 isplaced on the mask holder 130, as shown in FIG. 8E. Then, as shown inFIG. 8F, heat is applied from the pellicle holder 120 to the micro cones28 at the temperature higher than the threshold temperature Tg, in someembodiments. In other embodiments, the heat is applied from the photomask holder 100. As shown in FIG. 7C, the heat returns the shape of thecones to the original shape, thereby detaching the cones from thesurface of the photo mask 10. Then, as shown in FIG. 8G, the pellicleholder 120 moves down so that the photo mask 10 without the pellicle 20is placed on the mask holder 130.

FIGS. 9A, 9B, 9C and 9D show pellicle mounting and dismountingoperations in accordance with some embodiments of the presentdisclosure. In some embodiments, the micro structures are a plurality ofmicro fibers 28C made of magnetic elastomer (magnetorheologicalelastomer (MRE)), as shown in FIG. 9A. The magnetic elastomer includespolymeric matrix (base polymer) with embedded micro- or nano-sizedferromagnetic particles. In some embodiments, as shown in FIG. 9A, themicro structures have fiber shape and the average diameter of each ofthe micro fibers 28C is in a range from about 0.5 μm to about 500 μm,and is in a range from about 2 μm to about 200 μm in other embodiments.In order to mount the pellicle 20 to the EUV photo mask 10, the microfibers 28C are pressed against the surface of the EUV photo mask 10 suchthat the ends of the fibers are attached to the surface of the photomask 10, as shown in FIG. 9B. In some embodiments, the pressing force(pressure) is in a range from about 0.01 N/cm² to about 1.0 N/cm². Ifthe pressing force is smaller than this range the pellicle may not befixed to the EUV photo mask, and if the pressing force is larger thanthis range, the fibers may be bent and may not be fixed to the EUV photomask. In order to de-mount the pellicle 20 from the EUV photo mask 10, amagnetic field is applied to the micro fibers 28C to bend them as shownin FIG. 9C. As shown in FIGS. 9C and 9D, the micro fibers 28C are bentsuch that the ends of the fibers are detached from the surface of thephoto mask 10. Once the ends of the fibers 28C are detached by bending,the pellicle 20 can be easily de-mounted from the photo mask 10 withminimum pull force. As set forth above, a magnetic force is applied inthe de-mounting operation before or without applying a pulling force toseparate the pellicle 20 from the photo mask 10.

FIGS. 10A-10C and 10D-10F also show more details of pellicle mountingand dismounting operations, respectively, of FIGS. 9A-9D, in accordancewith some embodiments of the present disclosure.

In a mounting operation, as shown in FIG. 10A, a pellicle 20 issupported by a pellicle holder 120, and an EUV photo mask 10 issupported by a mask holder 130 in a pellicle mounting apparatus. In someembodiments, the EUV photo mask 10 is placed on the mask holder 130facing down and the pellicle is held by the pellicle holder 120 facingup. Then, as shown in FIG. 10B, the pellicle holder moves up toward thephoto mask 10 and further toward a mask retainer 100 so that the photomask 10 abuts the mask retainer. As shown in FIG. 9B, the ends of themicro fibers 28C are attached to the photo mask 10 during and as aresult of the movement of the pellicle holder 120. Then, as shown inFIG. 10C, the pellicle holder 120 moves down so that the photo mask 10with the pellicle 20 is placed on the mask holder 130.

In a de-mounting operation, the photo mask 10 with the pellicle 20 isplaced on the mask holder 130, as shown in FIG. 10D. Then, as shown inFIG. 10E, the pellicle holder 120 moves up toward the photo mask 10 withthe pellicle 20, and a magnet 140 (permanent or electro magnet) isplaced over the photo mask 10. As shown in FIG. 9C, by the magneticforce from the magnet 140, the plurality of fibers 28C are bent anddetached from the photo mask 10. Then, as shown in FIG. 10F, thepellicle holder 120 moves down so that the photo mask 10 without thepellicle 20 is placed on the mask holder 130.

FIGS. 11A, 11B, 11C and 11D show pellicle mounting and dismountingoperations in accordance with some embodiments of the presentdisclosure.

In some embodiments, the micro structures are a plurality of micro cones28D having a top disposed on the base layer 26 and a bottom, as shown inFIG. 11A. In some embodiments, the top of the cones has a width ordiameter W3 in a range from about 0.5 μm to about 500 μm, or in a rangefrom about 2 μm to about 200 μm in other embodiments. In someembodiments, the cone has a circular or an elliptical bottom in planview and in other embodiments, the cone has a rectangular or a squarebottom in plan view. In some embodiments, a ratio between the top widthW3 and the bottom width W4 (W4/W3) is in a range from about 1 (i.e.,column shape) to about 100 and is in a range from about 5 to about 20 inother embodiments.

In some embodiments, the micro cones 28D are made of a light responsiveelastomer, which changes its shape by the application of light. In someembodiments, the light responsive elastomer is a liquid crystallineelastomer.

In order to mount the pellicle 20 to the EUV photo mask 10, the bottomsof the micro cones 28D are pressed against the surface of the EUV photomask 10 such that the bottoms of the cones 28D are attached to thesurface of the photo mask 10, as shown in FIG. 11B. In order to de-mountthe pellicle 20 from the EUV photo mask 10, light having targetwavelength (e.g., ultra violet light, visible light or infrared light)is applied to the cones 28D before the pellicle 20 is pulled from theEUV photo mask 10 or without pulling the pellicle. As shown in FIGS. 11Cand 11D, by irradiating the cones with the light, the plurality of cones28D deform to decrease the contact area, and thus the ends (bottoms) ofthe cones are detached from the surface of the photo mask 10. Once theends of the cones 28D are detached, the pellicle 20 can be easilyde-mounted from the photo mask 10 with minimal pull force. As set forthabove, light is applied in the de-mounting operation before or withoutapplying the pulling force to separate the pellicle 20 from the photomask 10.

FIGS. 12A-12D and 12E-12G also show more details of pellicle mountingand dismounting operations, respectively, of FIGS. 11A-11D, inaccordance with some embodiments of the present disclosure.

In a mounting operation, as shown in FIG. 12A, a pellicle 20 issupported by a pellicle holder 120, and a EUV photo mask 10 is supportedby a mask holder 130 in a pellicle mounting apparatus. In someembodiments, the EUV photo mask 10 is placed on the mask holder 130facing down and the pellicle is held by the pellicle holder 120 h facingup. Then, as shown in FIG. 12B, the pellicle holder moves up toward thephoto mask 10 and further toward a mask retainer 100 so that the photomask 10 abuts the mask retainer. As shown in FIG. 11B, the ends of themicro cones 28D are attached to the photo mask 10 during and as a resultof the movement of the pellicle holder 120. Then, the pellicle holder120 moves down so that the photo mask 10 with the pellicle 20 is placedon the mask holder 130 as shown in FIG. 12C.

In a de-mounting operation, the photo mask 10 with the pellicle 20 isplaced on the mask holder 130, as shown in FIG. 12D. Then, as shown inFIG. 12E, light is applied to the micro cones 28 above the photo mask orbelow the photo mask 10. As shown in FIG. 11C, the light exposurechanges the shape of the cones, thereby detaching the cones from thesurface of the photo mask 10. Then, as shown in FIG. 12F, the pellicleholder 120 moves down so that the photo mask 10 without the pellicle 20is placed on the mask holder 130.

FIGS. 13A, 13B, 13C and 13D show pellicle mounting and dismountingoperations in accordance with some embodiments of the presentdisclosure.

In some embodiments, the micro structures are a plurality of microfibers 28E or micro cones as shown in FIG. 13A. In some embodiments, asshown in FIG. 13A, the micro structures have a fiber shape and theaverage diameter of each of the micro fibers 28C is in a range fromabout 0.5 μm to about 500 μm, and is in a range from about 2 μm to about200 μm in other embodiments. In order to mount the pellicle 20 to theEUV photo mask 10, the micro fibers 28C are pressed against the surfaceof the EUV photo mask 10 such that the ends of the fibers are attachedto the surface of the photo mask 10, as shown in FIG. 13B. In someembodiments, the pressing force (pressure) is in a range from about 0.01N/cm² to about 1.0 N/cm². If the pressing force is smaller than thisrange the pellicle may not be fixed to the EUV photo mask, and if thepressing force is larger than this range, the fibers may be bent and maynot be fixed to the EUV photo mask. In order to de-mount the pellicle 20from the EUV photo mask 10, ultrasound is applied to the micro fibers28C as shown in FIG. 13C. As shown in FIGS. 13C and 13D, the microfibers 28E are detached from the surface of the photo mask 10 by thevibration caused by the ultrasound. Once the ends of the fibers 28E aredetached by bending, the pellicle 20 can be easily de-mounted from thephoto mask 10 with minimal pull force. As set forth above, ultrasound isapplied in the de-mounting operation before or without applying thepulling force to separate the pellicle 20 from the photo mask 10. Insome embodiments, radio waves (e.g., microwaves) are applied to detachthe micro structures from the photo mask 10.

FIGS. 14A-14C and 14D-14F also show more details of pellicle mountingand dismounting operations, respectively, of FIGS. 13A-13D, inaccordance with some embodiments of the present disclosure.

In a mounting operation, as shown in FIG. 14A, a pellicle 20 issupported by a pellicle holder 120, and an EUV photo mask 10 issupported by a mask holder 130 in a pellicle mounting apparatus. In someembodiments, the EUV photo mask 10 is placed on the mask holder 130facing down and the pellicle is held by the pellicle holder 120 facingup. Then, as shown in FIG. 14B, the pellicle holder moves up toward thephoto mask 10 and further toward a mask retainer 100 so that the photomask 10 abuts the mask retainer. As shown in FIG. 13B, the ends of themicro fibers 28C are attached to the photo mask 10 during and as aresult of the movement of the pellicle holder 120. Then, as shown inFIG. 14C, the pellicle holder 120 moves down so that the photo mask 10with the pellicle 20 is placed on the mask holder 130.

In a de-mounting operation, the photo mask 10 with the pellicle 20 isplaced on the mask holder 130, as shown in FIG. 14D. Then, as shown inFIG. 14E, the pellicle holder 120 moves up toward the photo mask 10 withthe pellicle 20, and ultrasound is applied to the micro fibers. As shownin FIG. 13C, by vibrations caused by the ultrasound, the plurality offibers 28E are detached from the photo mask 10. Then, as shown in FIG.14F, the pellicle holder 120 moves down so that the photo mask 10without the pellicle 20 is placed on the mask holder 130.

FIG. 15 is a flowchart of pellicle mounting and dismounting operationsin accordance with some embodiments of the present disclosure. At S101,a pellicle is mounted on an EUV photo mask. In S103, the EUV photo maskwith the pellicle is used with an EUV lithography apparatus (e.g.,scanner) to fabricate patterns over a semiconductor wafer. Then, atS105, the pellicle is de-mounted from the photo mask. At S107, the photomask and the pellicle are subjected to cleaning and/or inspectionoperations. Then, in some embodiments, the photo mask is stored in amask stocker and/or a new pellicle is attached to the photo mask.

FIG. 16A shows a flowchart of a method making a semiconductor device,and FIGS. 16B, 16C, 16D and 16E show a sequential manufacturingoperation of a method of making a semiconductor device in accordancewith embodiments of present disclosure.

FIG. 16A shows a flowchart of a method of making a semiconductor device,and FIGS. 16B, 16C, 16D and 16E show a sequential manufacturingoperation of the method of making a semiconductor device in accordancewith embodiments of present disclosure. A semiconductor substrate orother suitable substrate to be patterned to form an integrated circuitthereon is provided. In some embodiments, the semiconductor substrateincludes silicon. Alternatively or additionally, the semiconductorsubstrate includes germanium, silicon germanium or other suitablesemiconductor material, such as a Group III-V semiconductor material. AtS201 of FIG. 16A, a target layer to be patterned is formed over thesemiconductor substrate. In certain embodiments, the target layer is thesemiconductor substrate. In some embodiments, the target layer includesa conductive layer, such as a metallic layer or a polysilicon layer; adielectric layer, such as silicon oxide, silicon nitride, SiON, SiOC,SiOCN, SiCN, hafnium oxide, or aluminum oxide; or a semiconductor layer,such as an epitaxially formed semiconductor layer. In some embodiments,the target layer is formed over an underlying structure, such asisolation structures, transistors or wirings. At S202 of FIG. 16A, aphoto resist layer is formed over the target layer, as shown in FIG.16B. The photo resist layer is sensitive to the radiation from theexposing source during a subsequent photolithography exposing process.In the present embodiment, the photo resist layer is sensitive to EUVlight used in the photolithography exposing process. The photo resistlayer may be formed over the target layer by spin-on coating or othersuitable techniques. The coated photo resist layer may be further bakedto drive out solvent in the photo resist layer. At S203 of FIG. 16A, thephotoresist layer is patterned using an EUV reflective mask with apellicle as set forth above, as shown in FIG. 16B. The patterning of thephotoresist layer includes performing a photolithography exposingprocess by an EUV exposing system using the EUV mask. During theexposing process, the integrated circuit (IC) design pattern defined onthe EUV mask is imaged to the photoresist layer to form a latent patternthereon. The patterning of the photoresist layer further includesdeveloping the exposed photoresist layer to form a patterned photoresistlayer having one or more openings. In one embodiment where thephotoresist layer is a positive tone photoresist layer, the exposedportions of the photoresist layer are removed during the developingprocess. The patterning of the photoresist layer may further includeother process steps, such as various baking steps at different stages.For example, a post-exposure-baking (PEB) process may be implementedafter the photolithography exposing process and before the developingprocess.

At S204 of FIG. 16A, the target layer is patterned utilizing thepatterned photoresist layer as an etching mask, as shown in FIG. 16D. Insome embodiments, the patterning the target layer includes applying anetching process to the target layer using the patterned photoresistlayer as an etch mask. The portions of the target layer exposed withinthe openings of the patterned photoresist layer are etched while theremaining portions are protected from etching. Further, the patternedphotoresist layer may be removed by wet stripping or plasma ashing, asshown in FIG. 16E.

As set forth above, the frame of the pellicle includes a plurality ofmicro structures. When the micro structures are attached to the photomask, the total contact area between the micro structures and thesurface of the photo mask is about 20% to about 60% of the total area ofthe bottom surface of the frame. Thus, there are plurality of air pathsformed between the pellicle frame and the photo mask, which suppressrupture of the pellicle or the photo mask when used in s pressurechanging apparatus. Further, in the foregoing embodiments, inde-mounting the pellicle from the photo mask, forces other than apulling forces are applied to de-mount the pellicle from the photo mask,no or a minimal pulling force to remove the pellicle from the photo maskis required, which also suppress rupture of the pellicle or the photomask. In addition, substantially no residue of adhesive material remainson the photo mask after the pellicle is removed, and thus no additionalcleaning process after demounting the pellicle may be necessary.Further, the demounted pellicle may be reused. In addition, photo masksneed are subjected to defect inspections periodically, and the maskinspection can be performed by using a non-EUV light source inspector,when a pellicle is demounted before the inspection without leaving glueresidues and particles, and then the pellicle is mounted back after theinspection. This inspection process does not require an expensive EUVlight source inspector to inspect mask with EUV pellicle.

According to some embodiments of the present disclosure, in a method ofde-mounting a pellicle from a photo mask, the photo mask with thepellicle is placed on a pellicle holder. The pellicle is attached to thephoto mask by a plurality of micro structures. The plurality of microstructures are detached from the photo mask by applying a force orenergy to the plurality of micro structures before or without applying apulling force to separate the pellicle from the photo mask. The pellicleis de-mounted from the photo mask. In one or more of the foregoing andfollowing embodiments, the plurality of micro structures are made of anelastomer. In one or more of the foregoing and following embodiments,the plurality of micro structures are a plurality of micro fibers. Inone or more of the foregoing and following embodiments, the applying theforce or energy comprises applying a pushing force to decrease adistance between the photo mask and the pellicle. In one or more of theforegoing and following embodiments, the micro fibers are made ofmagnetic elastomer, and the applying the force or energy comprisesapplying magnetic field. In one or more of the foregoing and followingembodiments, the applying the force or energy comprises applyingultrasound. In one or more of the foregoing and following embodiments,the plurality of micro structures are made of a shape memory elastomer,the plurality of micro structures are a plurality of micro cones eachhaving a top and a bottom disposed on an surface of the pellicle, andthe applying the force or energy comprises applying heat. In one or moreof the foregoing and following embodiments, the plurality of microstructures are made of a light responsive elastomer, the plurality ofmicro structures are a plurality of micro cones each having a topdisposed on an surface of the pellicle and a bottom, and the applyingthe force or energy comprises applying light.

In accordance with another aspect of the present disclosure, in a methodof mounting a pellicle from a photo mask, the photo mask is placed on aphoto mask holder, the pellicle is placed on a pellicle holder. Thepellicle includes a frame having an opening, and a plurality of microstructures are disposed on a bottom of the frame. The plurality of microstructures are attached to the photo mask by moving the pellicle holderso that the plurality of micro structures abut a surface of the photomask. The pellicle holder is moved to leave the photo mask with thepellicle on the mask holder. In one or more of the foregoing andfollowing embodiments, the plurality of micro structures are a pluralityof micro fibers made of an elastomer, and in the attaching the pluralityof micro structures, ends of the plurality of micro fibers are attachedto the surface of the photo mask. In one or more of the foregoing andfollowing embodiments, the elastomer is a magnetic elastomer. In one ormore of the foregoing and following embodiments, the plurality of microstructures are a plurality of micro cone made of a shape memoryelastomer, and in the attaching the plurality of micro structures, topsof the plurality of micro cones are attached to the surface of the photomask, and heat is applied to the attached plurality of micro cones. Inone or more of the foregoing and following embodiments, the plurality ofmicro structures are a plurality of micro cone made of an elastomer, andin the attaching the plurality of micro structures, bottoms of theplurality of micro fibers are attached to the surface of the photo mask.In one or more of the foregoing and following embodiments, the heat isapplied from a heater disposed in the pellicle holder. In one or more ofthe foregoing and following embodiments, the attaching the plurality ofmicro structures comprises detaching the photo mask from the mask holderand pressing the photo against a mask retainer.

In accordance with another aspect of the present disclosure, a pelliclefor an extreme ultra violet (EUV) photo mask includes an EUV transparentmembrane, a frame having an opening, and a plurality of micro structuresmade of an adhesive elastomer and disposed on a bottom of the frame. Inone or more of the foregoing and following embodiments, the plurality ofmicro structures are a plurality of fibers having an average diameter ina range from 0.5 μm to 500 μm. In one or more of the foregoing andfollowing embodiments, the plurality of micro structures are made of ashape memory elastomer. In one or more of the foregoing and followingembodiments, the plurality of micro structures are made of a magneticelastomer. In one or more of the foregoing and following embodiments,the plurality of micro structures are made of a light responsiveelastomer.

The foregoing outlines features of several embodiments or examples sothat those skilled in the art may better understand the aspects of thepresent disclosure. Those skilled in the art should appreciate that theymay readily use the present disclosure as a basis for designing ormodifying other processes and structures for carrying out the samepurposes and/or achieving the same advantages of the embodiments orexamples introduced herein. Those skilled in the art should also realizethat such equivalent constructions do not depart from the spirit andscope of the present disclosure, and that they may make various changes,substitutions, and alterations herein without departing from the spiritand scope of the present disclosure.

What is claimed is:
 1. A method of de-mounting a pellicle from a photomask, comprising: placing the photo mask with the pellicle on a pellicleholder, wherein the pellicle is attached to the photo mask by aplurality of micro structures; detaching the plurality of microstructures from the photo mask by applying a force or energy to theplurality of micro structures before or without applying a pulling forceto separate the pellicle from the photo mask; and de-mounting thepellicle from the photo mask.
 2. The method of claim 1, wherein theplurality of micro structures are made of an elastomer.
 3. The method ofclaim 2, wherein the plurality of micro structures are a plurality ofmicro fibers.
 4. The method of claim 2, wherein the applying force orenergy comprises applying a pushing force to decrease a distance betweenthe photo mask and the pellicle.
 5. The method of claim 2, wherein: themicro fibers are made of magnetic elastomer, and the applying force orenergy comprises applying magnetic field.
 6. The method of claim 2,wherein the applying force or energy comprises applying ultrasound. 7.The method of claim 2, wherein: the plurality of micro structures aremade of a shape memory elastomer, the plurality of micro structures area plurality of micro cones each having a top and a bottom disposed on ansurface of the pellicle, and the applying force or energy comprisesapplying heat.
 8. The method of claim 2, wherein: the plurality of microstructures are made of a light responsive elastomer, the plurality ofmicro structures are a plurality of micro cones each having a topdisposed on an surface of the pellicle and a bottom, and the applyingforce or energy comprises applying light.
 9. A method of mounting apellicle from a photo mask, comprising: placing the photo mask on aphoto mask holder; placing the pellicle on a pellicle holder, whereinthe pellicle includes a frame having an opening, and a plurality ofmicro structures are disposed on a bottom of the frame; attaching theplurality of micro structures to the photo mask by moving the pellicleholder so that the plurality of micro structures abut a surface of thephoto mask; and moving the pellicle holder to leave the photo mask withthe pellicle on the mask holder.
 10. The method of claim 9, wherein: theplurality of micro structures are a plurality of micro fibers made of anelastomer, and in the attaching the plurality of micro structures, endsof the plurality of micro fibers are attached to the surface of thephoto mask.
 11. The method of claim 10, wherein the elastomer is amagnetic elastomer.
 12. The method of claim 9, wherein: the plurality ofmicro structures are a plurality of micro cones made of a shape memoryelastomer, and in the attaching the plurality of micro structures, topsof the plurality of micro cones are attached to the surface of the photomask, and heat is applied to the attached plurality of micro cones. 13.The method of claim 9, wherein: the plurality of micro structures are aplurality of micro cones made of an elastomer, and in the attaching theplurality of micro structures, bottoms of the plurality of micro conesare attached to the surface of the photo mask.
 14. The method of claim13, wherein the heat is applied from a heater disposed in the pellicleholder.
 15. The method of claim 9, wherein the attaching the pluralityof micro structures comprises detaching the photo mask from the maskholder and pressing the photo mask against a mask retainer.
 16. Apellicle for an extreme ultra violet (EUV) photo mask, the pelliclecomprising: an EUV transparent membrane; a frame having an opening; anda plurality of micro structures made of an adhesive elastomer anddisposed on a bottom of the frame.
 17. The pellicle of claim 16, whereinthe plurality of micro structures are a plurality of fibers having anaverage diameter in a range from 0.5 μm to 500 μm.
 18. The pellicle ofclaim 16, wherein the plurality of micro structures are made of a shapememory elastomer.
 19. The pellicle of claim 16, wherein the plurality ofmicro structures are made of a magnetic elastomer.
 20. The pellicle ofclaim 16, wherein the plurality of micro structures are made of a lightresponsive elastomer.